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Commit 8bc661bf authored by Marek Roszko's avatar Marek Roszko Committed by Greg Kroah-Hartman
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tty/serial: at91: disable uart timer at start of shutdown 



The uart timer will schedule a tasklet when it fires. It is possible that it
can fire inside _shutdown before it is killed in the dma and pdc cleanup
routines. This causes a tasklet that exists after the port is shutdown, so when
the kernel finally executes it, it panics as the tty port is NULL.

This is a somewhat rare condition but its possible if a program keeps on
opening/closing the port. It has been observed in particular with systemd
boot messages that were causing a kernel panic because of this behavior.

Moving the timer deletion to the beginning of the function stops a tasklet from
being scheduled unexpectedly.

Signed-off-by: default avatarMarek Roszko <mark.roszko@gmail.com>
Cc: stable <stable@vger.kernel.org> # v3.12
[nicolas.ferre@atmel.com: modify commit message, call setup_timer() in any case]
Signed-off-by: default avatarNicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 3685f19e

drivers/tty/serial/atmel_serial.c

+10 −12
Original line number Diff line number Diff line
@@ -825,9 +825,6 @@ static void atmel_release_rx_dma(struct uart_port *port) 
	atmel_port->desc_rx = NULL;

	atmel_port->chan_rx = NULL;

	atmel_port->cookie_rx = -EINVAL;



	if (!atmel_port->is_usart)

		del_timer_sync(&atmel_port->uart_timer);

}



static void atmel_rx_from_dma(struct uart_port *port)
@@ -1229,9 +1226,6 @@ static void atmel_release_rx_pdc(struct uart_port *port) 
				 DMA_FROM_DEVICE);

		kfree(pdc->buf);

	}



	if (!atmel_port->is_usart)

		del_timer_sync(&atmel_port->uart_timer);

}



static void atmel_rx_from_pdc(struct uart_port *port)
@@ -1604,12 +1598,13 @@ static int atmel_startup(struct uart_port *port) 
	/* enable xmit & rcvr */

	UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);



	if (atmel_use_pdc_rx(port)) {

		/* set UART timeout */

		if (!atmel_port->is_usart) {

	setup_timer(&atmel_port->uart_timer,

			atmel_uart_timer_callback,

			(unsigned long)port);



	if (atmel_use_pdc_rx(port)) {

		/* set UART timeout */

		if (!atmel_port->is_usart) {

			mod_timer(&atmel_port->uart_timer,

					jiffies + uart_poll_timeout(port));

		/* set USART timeout */
@@ -1624,9 +1619,6 @@ static int atmel_startup(struct uart_port *port) 
	} else if (atmel_use_dma_rx(port)) {

		/* set UART timeout */

		if (!atmel_port->is_usart) {

			setup_timer(&atmel_port->uart_timer,

					atmel_uart_timer_callback,

					(unsigned long)port);

			mod_timer(&atmel_port->uart_timer,

					jiffies + uart_poll_timeout(port));

		/* set USART timeout */
@@ -1651,6 +1643,12 @@ static void atmel_shutdown(struct uart_port *port) 
{

	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);



	/*

	 * Prevent any tasklets being scheduled during

	 * cleanup

	 */

	del_timer_sync(&atmel_port->uart_timer);



	/*

	 * Clear out any scheduled tasklets before

	 * we destroy the buffers